The present invention relates to a transmission unit to be installed in a hybrid vehicle combining an engine and a motor, to obtain a driving force.
With improved fuel economy and lower emissions, hybrid vehicles benefit conservation of global environment and savings of limited resources. In a hybrid vehicle, a motor is arranged in series or parallel to an engine to assist the engine output and to serve as a generator for converting kinetic energy of the vehicle to electrical energy on deceleration.
A published Japanese patent application Publication (Kokai) No. 2000-9213 shows an apparatus for a hybrid vehicle. This apparatus includes a clutch chamber 101 defined by a first housing 113 and a first partition 116, a motor chamber 102 defined by a second housing 114, the first partition 116 and a second partition 117, and a transmission chamber 103 defined by a third housing 115 and the second partition 117, as shown in FIG. 6. The rotation of the engine is input to an electromagnetic clutch 110 in the clutch chamber 101, and the output of the electromagnetic clutch 110 is transmitted to a motor 111 in the motor chamber 102 and a transmission 112 in the transmission chamber 103 through an input shaft 100.
This input shaft 100 is rotatably supported by a bearing at each of support portions 120 and 121 which are provided in the third housing 115 and the second partition 117, respectively in a manner not to allow run-out and off-center deviation of the input shaft 100. On the sliding surface between the first partition 116 and the input shaft 100, there is provided a seal member 122 to prevent entrance into the motor chamber 102, of abrasion powder abraded from an electrode blush at a slip ring (or collector ring) 110a for supplying electric current to the electromagnetic clutch 110 in the clutch chamber 101, and moisture permeating from the joint surface between the engine and the transmission unit A.
The apparatus of the above-mentioned Japanese Publication has the following problems.
The clutch chamber 101 and the motor chamber 102 are in the dry state with no lubrication by oil. Therefore, the seal member provided therebetween requires the addition of a lubricating structure, specifically at its seal lip portion (to prevent powder produced by abrasion).
When a bearing requiring no lubrication structure is used as a seal member, the input shaft 100 is supported at three support points 120, 121 and 122 by the three bearings, as shown in FIG. 5A. In this three-point support structure including the bearing, as the seal member 122, rigidly supporting the input shaft without allowing radial motion, stress concentration is liable to occur at each support portions 120, 121 and 122 in the case of whirling motion of the input shaft 100 due to vibrations produced by the transmission 112. Consequently, the durability of the input shaft 100 and the bearings is decreased. (FIG. 5A shows the wavelike form of the input shaft exaggeratedly to illustrate the stress concentration.)
Moreover, when the support portions 120, 121 and 122 are to be assembled in this order, without providing a portion for absorbing the accumulated tolerance of constituent parts, as shown in FIG. 5C, the assembly operation of the third bearing portion 122 becomes unfeasible.
To improve the performance of the motor 111, the clearance between a rotor and a stator is set small, and there is a need for providing a predetermined clearance in addition to a part for absorbing the accumulated tolerance.
It is therefore an object of the present invention to provide a transmission unit for a hybrid vehicle which is capable of sealing an opening between a clutch chamber and a motor chamber without requiring a lubricating structure and without deteriorating the durability.
According to the present invention, a transmission unit for a hybrid vehicle comprises:
a unit housing defining a first dry chamber containing an electromagnetic clutch, a second dry chamber containing a motor, and a hydraulic wet chamber containing a transmission mechanism, and comprising a partition wall separating the first and second dry chambers;
an input shaft extending through the first dry chamber, the second dry chamber and the wet chamber, to input rotation from the electromagnetic clutch to the motor and the transmission mechanism;
first and second bearing members supporting the input shaft rotatably at first and second support points spaced from each other in the wet chamber, in a manner to prevent radial motion of the input shaft relative to the unit housing;
a third bearing member provided between the partition wall and the input shaft with a clearance interposed between the third bearing member and the partition wall, to allow radial motion of the input shaft relative to the unit housing; and
a seal member provided in the clearance, for preventing passage of foreign matters from the first dry chamber to the second dry chamber.